1. Field of the Disclosure
The technology of the disclosure relates generally to alignment, mounting, and radio frequency (RF) shielding of optical devices, including transmit optical sub-assemblies (TOSAs) and receive optical sub-assemblies (ROSAs), and related assemblies and methods. The optical devices may be employed in equipment in optical fiber-based distributed antenna equipment for distributing RF signals over optical fiber to remote units.
2. Technical Background
Wireless communication is rapidly growing, with ever-increasing demands for high-speed mobile data communication. As an example, so-called “wireless fidelity” or “WiFi” systems and wireless local area networks (WLANs) are being deployed in many different types of areas (e.g., coffee shops, airports, libraries, etc.). Wireless communication systems communicate with wireless devices called “clients,” which must reside within the wireless range or “cell coverage area” in order to communicate with an access point device.
One approach to deploying a wireless communication system involves the use of “picocells.” Picocells are radio frequency (RF) coverage areas. Picocells can have a radius in the range from a few meters up to twenty meters as an example. Combining a number of access point devices creates an array of picocells that cover an area called a “picocellular coverage area.” Because the picocell covers a small area, there are typically only a few users (clients) per picocell. This allows for minimizing the amount of RF bandwidth shared among the wireless system users. In this regard, head-end equipment and other equipment can be provided to receive incoming RF signals from a wired or wireless network. The head-end equipment distributes the RF signals on a communication downlink to remote antenna units distributed throughout a building or facility, hence providing a distributed antenna system. Client devices within range of the picocells can receive the RF signals and can communicate RF signals back to an antenna in the remote antenna units, which are communicated back on a communication uplink to the head-end equipment and onto the network.
The head-end equipment and other equipment in a distributed communication system may be optical fiber-based. In this regard, the equipment may be configured to convert electrical RF signals into optical RF signals to be communicated over optical fiber to the remote antenna units. Electrical-to-optical converters, such as a transmit optical sub-assembly (TOSA) optical device, may be employed in the head-end equipment to convert the electrical RF signals to optical RF signals and distribute the optical RF signals over downlink optical fiber to the remote antenna units. The remote antenna units receive the optical RF signals over the downlink optical fiber and convert these optical RF signals to electrical RF signals using optical-to-electrical converters to distribute the recovered electrical RF signals to client devices. Electrical RF signals received from client devices are likewise converted into optical RF signals using electrical-to-optical converters to distribute the optical RF signals over uplink optical fiber to head-end equipment. Optical-to-electrical converters, such as a receive optical sub-assembly (ROSA) optical device may be employed in the head-end equipment to convert the optical RF signals from the uplink optical fiber to electrical RF signals.
The optical devices (e.g., TOSAs and ROSAs) may be mounted or positioned on printed circuit boards (PCBs) provided in the head-end equipment to transmit and/or receive optical signals. Mounting or positioning of optical devices onto a PCB may limit the length of exposed, unshielded wire extensions between the optical devices and printed traces on the PCB to provide for signal integrity of the signals after conversion from optical to electrical signals. However, undesired losses can still be present. For example, mis-alignment of the optical devices to the PCB can result in power transfer losses between the connection of the optical device to electrical leads on the PCB. Further, RF interference that can occur between the electronic devices on the PCB and the optical device mounted thereto can result in higher signal-to-noise (S/N) ratios.